function dragElement(elmnt) {
  var pos1 = 0,
    pos2 = 0,
    pos3 = 0,
    pos4 = 0
  if (document.getElementById(elmnt.id + 'header')) {
    /* if present, the header is where you move the DIV from:*/
    document.getElementById(elmnt.id + 'header').onmousedown = dragMouseDown
  } else {
    /* otherwise, move the DIV from anywhere inside the DIV:*/
    elmnt.onmousedown = dragMouseDown
  }

  function dragMouseDown(e) {
    e = e || window.event
    // get the mouse cursor position at startup:
    pos3 = e.clientX
    pos4 = e.clientY
    document.onmouseup = closeDragElement
    // call a function whenever the cursor moves:
    document.onmousemove = elementDrag
  }

  function elementDrag(e) {
    e = e || window.event
    // calculate the new cursor position:
    pos1 = pos3 - e.clientX
    pos2 = pos4 - e.clientY
    pos3 = e.clientX
    pos4 = e.clientY
    // set the element's new position:
    elmnt.style.top = elmnt.offsetTop - pos2 + 'px'
    elmnt.style.left = elmnt.offsetLeft - pos1 + 'px'
  }

  function closeDragElement() {
    /* stop moving when mouse button is released:*/
    document.onmouseup = null
    document.onmousemove = null
  }
}
